While several of the genes that support the innate immune response have been identified through studies of natural mutations or gene knockouts, the great majority of these genes remain undiscovered. The Forward Genetics Core Laboratory will implement the goal of identifying most or perhaps all of the genes that subserve innate immunity. This goal will be achieved through the concerted production of novel mutations that impair innate immunity and through the mapping and isolation of those mutations that are created. Saturation mutagenesis will be accomplished in mice using N-ethyl-N-nitrosourea (ENU), a potent chemical agent that is known to produce chiefly A to G and A to T substitutions. Animals bearing mutations will be screened for phenotypic impairment of innate immune responses at the FI and F3 generations, to identify both dominant and recessive mutations of genes that are critical for innate immune responses. One screen to be employed relies upon a test of the ability to resolve infection of a type that is known to be contained entirely through innate immune mechanisms. In this acute model, a photometrically based assay of sepsis that depends upon extracorporeal detection of bacterial luminescence will be employed. Other screens measure the ability of host phagocytes to engulf and to kill microbes; the ability to respond to a battery of microbial inducers (PAMPs), and the ability to develop a state of tolerance to these inducers. Hence, a broad array of genes is tested, encompassing much of the functionality of the innate immune system. The Forward Genetics Core will interact particularly strongly with the Bioinformatics Core (which will pinpoint additional genes that appear to be involved in the innate immune response), the Molecular Biology Core, which will actively study mutations that are induced. Perhaps foremost, the Forward Genetics Core Laboratory will yield a rich harvest of mutants that will permit extensive genetic dissection of innate immune responses, and their failure in septic shock. These mutants will immediately be made available to the scientific community at large and simultaneously refined for positional cloning.